|The most fundamental property of a star is its mass. We have seen how mass dictates the evolution of a star, controlling its lifetime, end state, and which elements it makes by fusion. So how do we measure mass? The most fundamental way is to use binary stars: two stars orbiting each other under their mutual gravitational attraction. By observing properties of the binary such as the orbital period and the separation of the stars, we can learn about the masses of the stars. About half of the points of light that we see when we look up into the night sky are not single stars like our Sun but rather the combined light from two or more stars orbiting each other. For example, the three closest stars to our Sun (remember the parallax and H-R Diagram labs?), alpha Centauri, alpha Centauri-B, and Proxima Centauri are an example of a triple system.|
In this lab you will find out how astronomers learn about stars by studying binary stars. You will also learn how astronomers find extrasolar planets using techniques that are similar to those they use to observe binary stars. You will use some of these techniques to learn about various properties of stars and extrasolar planets.